The invention relates to a method of preparing items to be mailed, in which periodically at least one main document is inserted into an envelope by means of a mail preparation system comprising an inserter station, and in which a printing is printed on an envelope by means of a printer, which printing corresponds to a given main document.
Such a method is known from European patent specification 0 265 192, in which the given main document with any enclosures is inserted into an envelope and that envelope is provided with a printing corresponding to that main document.
A problem involved in such a method is the printability of the envelopes which sets limits to the printers that can be used, and to the thickness, the dimensions, and the stability of the documents and enclosures to be inserted into the envelopes. The envelopes have a relatively large thickness which varies with the contents, and the surface to be printed yields to pressure exerted on it, depending on the contents inserted. This problem is enhanced when in a run successive envelopes are to be supplied with different numbers of document sheets and enclosures.